1. Field of the Invention
This invention relates to semiconductor lasers and heat sink assemblies therefor. More particularly, this invention relates to conductively cooled laser diode arrays containing a multiplicity of individual laser diodes.
2. Description of the Prior Art
Semiconductor injection laser diodes have many advantages. Their small size and mechanical stability have suggested their use in a variety of harsh environments which had previously excluded the use of other types of laser devices. The dimensions of an individual injection laser diode are typically submicron to a few microns across and usually no more than a fraction of a millimeter in length. The injection laser diodes are also capable of extremely high efficiencies compared to other types of lasers and may be used either in continuous or pulsed modes.
However, the efficient operation of an injection laser diode requires the dissipation of relatively large amounts of heat. In particular, in the case of a solid state laser rod pumped by emissions from either light emitting diodes or injection laser diodes, dissipation of heat from the diodes themselves becomes critical to both efficiency and the longevity for the individual diodes in the arrays. Since each individual diode is quite small, it becomes necessary to closely pack a plurality of individual diodes into arrays in order to generate the required amounts of input power to the larger pumped solid state laser rod in such situations. However, with increased packing densitities of the individual diodes, the space available for extraction of heat from the individual diodes necessarily decreases, thereby aggravating the problem of heat extraction from the arrays of individual diodes. One solution that has been proposed in the past is to circulate a chilled fluid past the diodes in the arrays, often by pumping the chilled fluid through cooling passages within the arrays themselves. However, this solution greatly increases the cost, weight, and power consumption of the overall laser diode array assembly with an attendant overall decrease in system reliability due to the presence of the added cooling subsystem mechanisms. Also, the presence of the chilled fluid requires a stabilized lower temperature condition for the consistent operation of the overall laser system, which, in turn, requires cool down period prior to operation of the system. One such liquid cooled laser diode array is disclosed in U.S. Pat. No. 4,315,225 to Allen et al. Conductively cooled laser diode array assemblies have also been proposed, but none have been capable of handling the high heat flows generated by high output injection laser diode arrays.